1. Field of the Invention
This invention relates to restraint systems and seat systems for protecting the crewmembers of an aircraft from high "g" forces resulting from aircraft maneuvers and/or emergency ejections from aircraft.
Modern high performance fighter aircraft are capable of flight maneuvers which subject the crewmembers to very high forces of acceleration. Severe stresses are placed on the crewmembers by such aircraft maneuvers. Indeed, many modern aircraft are capable of aerial maneuvers which are beyond the tolerance of the human crewmembers. Consequently, fighter aircraft and their crewmembers are occasionally lost as a result of pilot blackout.
Aircraft equipment malfunction or adverse environmental conditions may occasionally make proper control of the aircraft so difficult as to render it improbable that the aircraft can be safely landed. Enemy fire in combat situations may seriously disable an aircraft or crewmember making it also improbable that the aircraft can be brought to a safe landing. In such situations, ejection of the crewmembers from the aircraft may be desirable. However, in some such situations, the high forces of acceleration generated by catapult ejection systems may be added to the forces generated by the motion of the aircraft and the total forces may thus exceed the tolerance of the crewmember. Consequently, pilots and their crewmembers are occasionally killed or severely disabled as a result of ejection from an aircraft.
2. Statement of the Prior Art
Many prior art methods of protecting the crewmember from the stresses of "g" forces require that the crewmember be placed in a prone position. This position purportedly allows the crewmember to be better able to tolerate "g" forces to which the crewmember is commonly subjected as a result of many types of aircraft maneuvers. However, this prone position reduces the pilot's visibility and also may make it more awkward for the pilot to operate the controls. In addition, such a position makes it more difficult to safely eject the crewmember in the event of an emergency due to the dimensions of the seat required, and there is an increased probability that the excessive length of the seat will make it more likely that the seat will tumble as a result of the wind blast after ejection. An example of such prior art seating systems in U.S. Pat. No. 2,369,258 to Shebat.
Other prior art seating systems for aircraft provide the capability of altering the seating position (and sometimes the seating position angle as well) of the pilot or crewmember as required for various conditions of flight. Such systems thus place the crewmember in a leaned back position to enhance "g" tolerance in order to perform certain aircraft maneuvers. Such systems also allow the crewmember to be in a nearly upright seated position when flight conditions require the crewmember to have good visibility and improved dexterity in operating the controls. However, the disadvantage with such systems is that powering the seat to so alter its position adds to the complexity of the seating system and its weight; moreover, movement of the seat to a desired position may not be fast enought to accommodate flight requirements, particularly under combat conditions. Another disadvantage with these systems is that they are unable to accommodate many flight conditions where, in many instances, good visibility and "g" protection are required simultaneously. Two examples of such prior art seating systems are U.S. Pat. No. 4,243,024 to Crosby and U.S. Pat. No. 4,004,763 to Bunnell.
Systems which are fixed in the layback position also have the disadvantage that they reduce the pilot's visibility both within and outside the cockpit and sharply decrease the available display panel area. Moreover, many crewmembers instinctively go to an "alert" body position--head erect and torso crouched forward - during the high stress situations where the "g" protection is needed the most. Moreover, studies have shown that crewmembers have a lower tolerance to vibrations, which are typical during high aircraft acceleration, in the supine position. An example of such restraint systems in U.S. Pat. No. 3,329,464 to Barwood.
Other prior art systems for providing protection from "g" forces to the crewmember include strap restraints retaining the pilot or crewmember firmly against the seat. Such prior art systems typically provide restraint to the crewmember while in a supine or erect seated position. Such restraint systems severely limit the degree of movement of the crewmember in the seat.
Some prior art systems use a pad positioned over the chest of the crewmember to apply restraint directly to the crewmember's chest. Although such chest pads tend to spread out the restraint forces over the crewmember's chest, they are functionally essentially the same as and thus no more effective than the restraint systems described hereinabove. Two examples of such prior art restraint systems using chest pads are U.S. Pat. No. 3,524,679 to De Lavenne and U.S. Pat. No. 4,300,799 to Cunningham.
Still other types of prior art systems for protecting crewmembers from "g" forces incorporate suits filled with pressurized air. The pressurized air within the suit exerts pressure at certain areas of the crewmember's body such as the abdomen and legs to prevent the crewmember's blood from pooling in these areas of the body as a result of high "g" forces. The disadvantage with such pressurized suits is that they fail to deal with the problems of compressive forces exerted on the spine by the "g" forces as well as local pressure points located where the crewmember's body contacts the seat. An example of such prior art air pressure suits incorporating automatic pressure regulation therein is U.S. Pat. No. 4,243,024 to Crosbie.
A high "g" protection system is thus needed that will provide protection against compression of the vertebrae of the spine caused by the forces of acceleration as well as generally improve the crewmember's tolerance to the forces of acceleration while allowing for selective crewmember movement, good visibility, safe ejection and good access to the controls.